The present invention relates to a variable attenuation device intended to be inserted between a transmitter circuit having a certain internal impedance and a load circuit, this device being composed of at least one parallel attenuation branch made up from a variable resistance component (p-i-n diode) and a bias circuit to vary the resistance of the component as a function of an attenuation control variable.
Such devices are well known and have important applications, in particular as an amplitude modulator for a radio transmitter, where the modulation functions as an attenuation command variable. In this type of application, in order to obtain a good dynamic range of modulation, attempts are made for it to be possible to handle relatively high power outputs from the transmitter circuit.
The known attenuation devices, for example that described in U.S. Pat. No. 4,009,456, are not suitable for handling large power outputs.